
public class Test {
    public static void main(String[] args) {
        String a="12+";
        int i=0;
        char c=' ';
        do{
            if ((c=a.charAt(i))<48){
                System.out.println("c不是数字");
            }
            System.out.println(c);
            i++;
        }while (i<a.length());
    }
}
